Denoios

Hello!

I have an issue with my brand new gravel bike.
I ordered a Cannondale Topstone 1 with a Shimano GRX system. The bike was delivered by mail and once unpacked and gone for a ride I noticed, that the chain rubs on the front derailleur when in the topmost gear.
So I set it up again, reseated the cable, adjusted the tension, adjusted the H/L screws and all according to Shimanos manual (see 'Shimano GRX 810 front derailleur manual' on Google, first result - I sadly couldn't post the link).
Then after installing everything according to the manual, the topmost gear was rubbing intesively on the outer side of the cage.

Well, I thought, maybe something is incompatible here.
I'd rather be able to use the topmost gear than the lowest gear on the largest chainring. So I adjusted the H screw accordingly to stop it from rubbing against the cage.
But I couldn't. Through one chain rotation the chain sways from left to right by roughly 4mm, making it rub on the left side at one point and on the right side at another point.

My questions now:
Has someone of you ever encountered this and is there something I can (or should) do?
Or should I rather go to the dealer and return the bike?
Do you have an idea what the reason could be?

Thanks a lot in advance!
Best Regards,
Daniel

KCT1986

You mean 1 rotation of the chainring right?

That much 'wobble' in the chainring seems excessive for a new crankset.

Does it seem that there is excessive play between crank/bottom bracket and the BB shell?

Kontact 

Is the the crank "loose", where you can make it swing back and forth without turning the crank, or is the chainring "out of true", like a wheel?

Either way, I wouldn't ride it and get whoever sold it to you to service it.

cobba

Cross chaining?

TiHabanero

4mm variance is quite a bit and is likely out of spec for the crankset/BB. Needs to go back to the dealer and have them determine the fix under warranty.

Kai Winters

Who built the bike? Sounds like you did. If so I'd not trust the build/set up as your post sounds like you aren't experienced building a bike out of the box.
Take it to a shop and have them go over it.
If what your saying is accurate and the bike is set up and adjusted correctly then it could be a warped chain ring if the rubbing is and off then on action. Kind of unlikely but possible.
New in a box bike does not mean it is ready to ride.
You need to have someone experienced and knowledgeable evaluate the bike...or not...as you like.

Denoios

I wish it was cross chaining, but no. I was in big/small (or the gear that allows you to go the fastest. And it was touching both, the inner and outer side of the cage.

I tried to determine both of your questions and: It's not loose as far as I can tell. But the chainring is definitely out of true, when turning the crank I could see the chainring in the front move left/right. Thanks for the tip! That allows me to tell them exactly what is wrong.

Yes, I meant 1 rotation of the chainring. I could not induce any movement by hand, so that seems to be fine at least... But as mentioned above it seems to be the chainring is out of true...

----

Thanks for all your answers! They helped a lot!

I'll drop the dealer a message and come back here for an update

Denoios

No I did not build it myself. I only set up the bike out of the box, which, in this case, was tightening bolts with a torque wrench. I am sorry if my missing language skills lead you to believe I am not able to do so.
Thanks to a previous reply I did take a look at the chainring and it is indeed warped, not by much, but enough for the chain to rub on both sides of the cage throughout one rotation. So your guess is correct!
Like you, I did not assume that to be the case which is why I did not take a look at it earlier.

Thanks for your help!

dedhed

How did the box look? Sounds like shipping damage

Andrew R Stewart 

i have yet to meet a boxed bike that didn't need some fine tuning to work well. This need is but one reason why many brands still only sell through a LBS. But each company can choose to control their reputation and product liability and balance that against greater sales and/or profit the way they are happy with. Just as the consumer can decide what is of greater importance, a well working bike with a local expert backing it up or saving some cost. Andy

Denoios

You might not agree with me on this one, but getting a bike delivered with a fitted BB and chainring, I expect these two components to be installed correctly and not needing reinstallment. Otherwise whats the point in sending a pre-built bike if you have to take integral parts apart as soon as you unpack it?
I know the entire transmission is a delicate system which requires constant readjustment throughout use. This is exactly the reason why I started to adjust the FD and RD.

My comment about just needing to tighten a few bolts after unpacking might have sounded a bit naive, but I was also a bit salty regarding Kai's answer. Sorry for that one.
I just find it odd to get 'go to a bike shop' as one of the first suggestions. It feels to me like gatekeeping the skill to set up a bike instead of sharing ones knowledge.

Trakhak

You're pretty good at gatekeeping yourself.

Your alternatives, all of which have been mentioned at least once:

Send the bike back for repair or replacement.

Take the bike to a shop for repair.

Fix it yourself.

I'd go with fixing it yourself. The chainwheel is thin metal, which is why it's so easy to bend. Use a large adjustable wrench for the bending operation. Sight down the front derailleur cage to locate the places where the chainring is out of true. Gently bend the chainring until it's true.

That's how to true the outer chainring. In the majority of cases, that's the only ring that's out of true. If you have two-chainring crankset and the inner ring is also out of true, and is out of true in exactly the same locations as the outer ring, then it's the crankset that's off.

soyabean

There is so much FREE knowledge out there, but no one wants to learn any of it.

One example, Park Tools sells tools to fix bikes AND they make Yt videos on how to use them.

I got my experience from reading books, wrenching in bike shops, and flipped about 1000 bikes, still counting.

So put it the hours to learn something, or pay your LBS to fix it.

Most folks can't fix their cars, plumbing, roofing, and even bikes, and that's totally normal and acceptable.

Denoios

Interesting perspective!

I have read all of the answers above and I am very thankful for all of your support! I am not disagreeing with or dismissing any of your answers.
I will write a message to the dealer and ask on how we move further.

What I meant by gatekeeping is, that some of the answers are 'go to a bike shop and get it set up', assuming that the problem I described is because I did not set it up correctly.Regarding your instructions, thanks for telling me! But as some have suggested, I will return it to the dealer or have it fixed, whatever the dealer is fine with.

Thanks a lot again!

Kontact 

It may be worth removing the chainring. Sometimes they are warped because they were screwed down unevenly. Sometimes they are just bent and it is easy to see and correct when you place them on a glass or granite counter. And sometimes the problem is the spider arms not being true, which you can see by removing the rings, holding the seat tube and using your finger as a runout measure - all 4 or 5 spider arms should brush the end of your finger equally as you rotate the crank. I've seen all three on new bikes.

Being able to describe where the problem lies will avoid getting the wrong solution from the seller.

smd4

Of course it’s assumed that you didn’t set it up correctly! Because 99% of cyclists don’t know how to set up a bike, let alone adjust it. The very idea that you came to an internet site looking for solutions to your problem identifies you as someone with perhaps not a great understanding of bike mechanics. The suggestion to take it to a bike shop isn’t gatekeeping. It’s just the best suggestion for someone who bought a new bike which is under warranty.

I don’t understand why people have to be offended if their bicycle mechanic skills are called into question. Is it because we still, deep down, think of bikes as nothing more than simple kids toys? If I went to an electrician’s forum asking why my light switch didn’t work, would I be offended if the members told me to call an electrician? Of course not.

Andrew R Stewart 

My near 50 years of working your LBS makes me have the opinions and experiences I express here. The bike industry has shipped partially assembled bikes for decades, to bike shops for that last bit of assembly AND the tuning that specific bike in the state of assembly that it saw leaving the factory needs. The bike that comes out of a box and truly only needing pedal, seat and ft wheel installing and no other tweaking or double checking is the rare one. Of course the on line ad for a bike won't want to say this... their job is to try to get you to buy the bike and not much else. There are a few on line resellers that claim to do their own "out of the factory box assembly, test check and repacking" before they will ship the bike out. Still we see more than a few of these every spring with "my gears don't work" or "my disk brakes rub" or "my crank makes a noise" or some other example of poor previous work and/or a lack of after the initial rides a rechecking of the adjustments.

The cost of delivery (the bike's fabrication, assembly, warehousing, shipping) is higher than most think and many brands do whatever they can to reduce these costs, often at the expense of the workers' pay. This labor cost is a very big reason why many bike factories are located in countries known for their cheap labor. Well I hate to burst a bubble but one gets what one pays for, for the most part. Now if you remove the feedback loop and the final pro check over of a bike and make it harder for the ultimate rider to return defective stuff (repacking and shipping off) why would it be a surprise that the assembly quality would be less than what your LBS would deliver to you?

All this won't get your bike working well though. The possible issue has been talked about, a loose/bent/damaged chainring/BB is one that is hard for us to get a real idea of since we don't have the bike (or even good video) in front of us. An experienced eye can tell this stuff pretty quickly and perhaps help explain the issue far better than we can long distance.

Ft ders can be about the most frustrating device to adjust well on a bike. Good luck. Andy

Kai Winters

Regardless of the cost of the bike...they all need adjusting after they come out of the box and are 'assembled'...

wheelreason

Something between the BB shell and the chainring is off (stop blaming the chain). Most times it's in the chainring or it's mounting. First thing is to figure out what the issue is, then depending on that, approach the repair/adjustment accordingly. In this case being a new bike, I'd let the "vendor" (see what I did there?) handle it. About 10% of new bikes coming out of the box require some "tweeking" beyond assembly and adjustment, and a few are destined for return to the manufacturer.

bikemike73 

Sounds like the OP has the answer to this issue.
Great video !!
Thanks for sharing !!!

Denoios

I understand. I would disagree with your comment about coming to an internet site. Isn't this the exact reason for this subforum? Of course you can't provide me with a solution, meaning you repair the bike for me. But you all shared your knowledge in this regard which is what I was looking for and in the end help me solve this issue.

---

To give the promised update on this thread.
I did find the solution, but also one other problem with the bike that is somewhat connected to the problem described initially.
The shifter cables for the FD and RD are twisted around each other within the frame, like a twisted pair wire. This makes the FD move, when releasing tension for the RD. This in turn makes it impossible to set the tension and L/H screws correctly.
The chain falls off the chainring, depending on the RDs position, because the FD cage moves when moving the RD.
The problem with the BB/crankset being not mounted correctly makes the chain rub on the cage, even when disconnecting the shifter cable and just moving the cage using the L screw, just adding to the issue with the shifter cables.

Furthermore after digging through videos from ParkTool about things I usually not do on a bike I noticed the handlebar is incorrectly wrapped. But thats just a minor issue.

Your posts helped me to describe the problem to the dealer. He agreed to take it back and replaces it with a (hopefully) correctly mounted one.

Thanks a lot again!
Kind Regards,
Daniel

SJX426 

@Denoios - so the chain set was good? The problem was the movement of the FD when the RD was used?
How can the chain move 4mm side to side without adjusting the RD or FD?

Denoios

Unfortunately not. the crankset/BB is incorrectly installed making all chainrings move left/right, in reference to the frame, especially under load.
What I meant by the chain moving by 4mm, is that it moves sideways on the chainring (because the chainring moves/wobbles sideways). Sorry for the confusion.
But as someone pointed out, it is likely to be the BB or the crankshaft as both chainrings are moving side to side at the same time.

smd4

Indeed it is! It's precisely for people like you--riders with questions on bike repair. I suspect that probably no competent bike mechanics are asking questions on this subforum.

The advice you were given was correct, given how new the bike was.

Crankycrank

I will say that most of the time when someone has an issue with a new bike, no matter how advanced their skills are, it's just a wise thing to do to take it to the shop to fix as any sign that you or someone else worked on it leads to suspicion by the shop and possible refusal to do the fix for free because it may appear you caused the damage. Bike shops face this issue all the time and often lose money fixing what customers have damaged themselves and lie about it. Nothing personal on you, just the reality of the bike business.